My EIGRP Troubleshooting Flashcard

Key things about EIGRP Neighbour Process

The following should match:

• Hello Types
• K-value
• AS Number
• IP Subnet
• Hello Interval
• 60 Seconds for low speed NBMA
• 5 Seconds for all other interfaces

Multicast Hellos

• 224.0.0.10 ( 0100.5e00.000a)

EIGRP DUAL Routing Algorithm Concepts

• Feasible Distance ( FD) is the minimum distance (Metric) along a path to a destination Network.
• Reported Distance (RD) is the distance towards a destination as advertised by an upstream neighbour.
• A neighbour meets the feasibility condition (FC) if the reported distance by a the neighbour is smaller than the feasible distance (FD ) of this router.
• Command Used to find out FD
• Show ip eigrp topology all-links

EIGRP DUAL Routing Algorithm – Active Process

• Normal (stable) state of a route is passive

• Going active is the normal process for resolving network topology changes

Route becomes active if it is lost (or metric increases) and there aren’t any feasible successors

Going active means sending Queries to neighbours looking for an alternative path.

• SIA-Queries are sent to a neighbour up to three times

May Attempt to get a reply from a neighbour for a total of 6 minutes.
If still no Reply by the end of this process, consider the route stuck through this neighbour.

• On the router that doesn’t get a reply after 3 SIA-queries:

Reinitialize neighbour who dint answer.
Goes active on all routes kown through bounced neighbour.
Re-advertises to bounced neighbour all routes that we were advertising.

Likely causes of Stuck-in Active (SIA)

• Bad or congested links.
• Query Range is too long
• Excessive redundancy
• Overloaded router (high CPU)
• Router memory shortage
• Software defects
• Minimising SIA Routes
• Decrease query scope (involve fewer routers in the query process)
• Summarisation (manual or auto)
• Distribute-lists
• Define remote routers as stubs
• Run a Cisco IOS which includes the fix for CSCdp33034